Novel sulfur compound modifiers for chloroprene polymerization

ABSTRACT

R3 and R4 are selected from the group consisting of hydrocarbon radicals having from 1 to 8 carbon atoms or hydrogen with at least one of R3 and R4 not being hydrogen and n is 1 to 4.   or   where X, Y and Z are selected from the group consisting of oxygen and sulfur, R1 is a hydrocarbon radical having from 1 to 8 carbon atoms, R2 is a hydrocarbon radical having from 1 to 8 carbon atoms or is a radical the same as   or   Chloroprene is polymerized in the presence of compounds of the formula

United States Patent [191 Edmondson Dec. 2, 1975 [75] Inventor: Morris S. Edmondson, Alvin, Tex.

[73] Assignee: Petro-Tex Chemical Corporation,

Houston, Tex.

[22] Filed: Jan. 15, 1975 [21] App]. No.: 541,237

Related US. Application Data [63] Continuation-in-part of Ser. No. 289,521, Sept. 15,

1972, abandoned.

[521 U.S. Cl. 260/923; 260/843 '[51] Int. C13... C08F 136/16; C08F 4/00 [58] Field of Search... 260/29.7 SQ, 29.7 NC), 92.3, 260/843, 84.1

[56] References Cited UNITED STATES PATENTS 2,264,173 11/1941 Collins 260/923 X 3,190,865 6/1965 Miller 260/923 3,472,828 10/1969 Montgomery... 260/923 3,507,825 4/1970 Paris 260/923 X 3,808,183 4/1974 Branlard 260/923 3,810,856 5/1974 Dalhuisen et al. 260/923 X 3,838,140 9/1974 Mayer-Mader et al. 260/923 OTHER PUBLICATIONS D. Twiss, A Study of Aliphatic Polysulfides, J. Amer. Chem. Soc., Feb. 1927.

Primary Examiner.loseph L. Bohofer Assistant Examiner--Herbert J. Lilling Attorney, Agent, or FirmN. Elton Dry; Kenneth H. Johnson [57] ABSTRACT Chloroprene is polymerized in the presence of compounds of the formula Y 1 ll N- ..R2 R4/ Z S where X, Y and Z are selected from the group consisting of oxygen and sulfur, R, is a hydrocarbon radical having from I to 8 carbon atoms, R is a hydrocarbon radical having from 1 to 8 carbon atoms or is a radical the same as R and R are selected from the group consisting of hydrocarbon radicals having from 1 to 8 carbon atoms or hydrogen with at least one of R and R not being hydrogen and n is 1 to 4.

4 Claims, No Drawings NOVEL SULFUR COMPOUND MODIFIERS FOR CHLOROPRENE POLYMERIZATION This application is a continuation-in-part of Ser. No. 289,521, filed Sept. 15, 1972, and nowabandoned.

It has been known to polymerize chloroprene in the presence of sulfur compounds as polymerization modifiers. Mercaptan compounds have been extensively'employed aspolymerization modifiers. Early patents for the polymerization of hydrocarbon derivatives and copolymers such as the polymerization of butadiene with styrene suggested that sulfur compounds could be employed with the invention being that a combination of a mercaptan and a xanthogen compound is used. For example U.S. Pat. No. 2,401,346 and U.S. Pat. No.

where X, Y andZ. are selected from the group consisting of oxygen and sulfur, R is a hydrocarbon radical having from 1 to 8 carbon atoms, R is a hydrocarbon radical having from 1 to 8 carbon atoms or is a radical the same as R and R, are selected from the group consisting of hydrocarbon radicals having from 1 to 8 carbon atoms or hydrogen with at least one of R and R, not being hydrogen and n is l to 4. Compounds of this type may be formed e.g. as disclosed in Twiss, W. D. JACS 49, Feb. 1927, p. 491-4. Forconvenience these compounds will be referred to as the sulfur modifiers in this application.

According to this invention polymers of chloroprene, 2-chloro-l,3 butadiene, are polymerized using the sulfur modifiers as a polymerization modifier. The term polymers of chloroprene encompasses polymers in which chloroprene is the major or predominant monomer. Comonomers may also be employed such as 2,3- dichloro-l, 3-butadiene; acrylonitrile, methyl methacrylate and so forth. Usually, the total amount of comonomers will represent no greater than 25 mol percent of the total monomers and preferably will constitute less than 15 mol percent of the total monomers including chloroprene. The polymerization of chloroprene in aqueous emulsion is well known and any such system which does not interfere with the novel characteristics of this invention can be employed. Processes and methods for the polymerization and recovery of chloroprene are disclosed, for example, in Encyclopedia of Polymer Science and Technology, Vol. 3, page 705-730 (Interscience, 1965) and in numerous patents such as U.S. Pat.'Nos. 2,264,173 and 2,264,191 both issued on Nov. 25, 1941 The polymerization may be conducted either batch or continuously.

Conventional emulsifiers may be employed such as the salts of rosins and rosin derivatives such as wood rosin, disproportionated rosin or hydrogenated rosin; ammonium, sodium or potassium salts of long chain fatty acids; nonionic surface active agents such as the ethylene oxide or propylene oxide condensation products of compounds containing reactive hydrogen atoms. Additional emulsifying agents are disclosed in U.S. Pat. No. 2,264,173. In this specification rosin or rosinates include the various commercial rosins, the dehydrogenated rosins and disproportionated rosins and salts thereof. Rosin base emulsifiers are well known to the art. A particularly preferred rosin emulsifier is a disproportionated wood rosin, purified by distillation (sold by the Hercules Powder Company as Resin 73 l- S).

The pH of the aqueous emulsion for polymerization may be varied depending upon the particular emulsifi: cation system employed and can be acidic, neutral or alkaline; however, it is preferred to have a pH in the range of about 7 to 13.5. ,7

Conventional catalysts for chloroprene polymerization may be employed and preferred catalysts are peroxide catalysts of the organic or inorganic type. Examples of organic peroxides arebenzoyl peroxide, cumene hydroperoxide, tertiary-butyl isopropylbenzene hydroperoxide, azo catalysts such as alpha-alpha -azo-bisisobutyronitrile and the like. Suitable inorganic peroxides are such as inorganic per acids including per sulfates, perborates or percarbonates e.g. ammonium or potassium per sulfate and hydrogen peroxide. The catalyst may be used in amounts required to bring about polymerization at any desired rate with suitable ranges being from 0.001 to 0.5 parts by weight per parts of polymerizable monomer.

The usual methods may be employed to prepare an aqueous emulsion of the monomeric material and emulsifying agent and water. The proportions are not critical but generally the monomer will be present in an amount such as from 30 to 60 percent by weight based on the total weight of the composition.

The sulfur modifier may be fed during polymerization. The only requirement is that the sulfur modifier be present for polymerization modification. However, it is usually preferred to add at least the predominant portion of the sulfur'modifier to the initial polymerization charge. Although the amount of sulfur modifier is not critical certain proportions have been discovered to give s'uperior'results and within the range if from about 3 0.05 to 5 parts by weight of the sulfur modifier per 100 parts of polymerizable monomers are usually employed with a preferred range being from about 0.2 to 1.5 parts per 100 parts of monomer.

Other modifiers or other agents may be present in the emulsion. For instance, the polymerization may be carried out in the presence of sulfur to produce a sulfur modified polychloroprene. Also, chain transfer agents may be employed such as the alkyl mercaptans, e.g. dodecyl mercaptan, iodoform and benzyl iodide. However, compounds which will interfere with the proper functioning of the sulfur modifier should be avoided and thus the modifier may consist essentially of the sulfur modifiers of this invention. At any rate preferably the modifiers will be predominately by weight of the sulfur modifier compounds of this invention.

Normally, the polymerization would be conducted in an oxygen free or substantially oxygen free atmosphere such as use of an inert gas. However, in some processes a controlled amount of oxygen is employed.

The degree of polymerization and characteristics of the polymer can be controlled as is known in the art. The production of either benzene soluble or benzene insoluble polymers is within the scope of this invention. Suitable ranges for the percent of monomer conversion are such as between 60 and 90 percent conversion. The products can be employed to produce easy processing blends such as disclosed in US. Pat. No. 3,655,827 with the modifiers of this invention being used in preparation of either the so] or gel polymers or both but preferably in the preparation of the sol portion of the blend. If the sols are so modified with the sulfur modifiers a preferred range of modifier is from 0.10 to 3 weight parts per 100 parts of total monomer.

The temperature of polymerization may be varied depending upon the paticular type of polymer being employed with suitable ranges being from C. to 90C. with the preferred range being between 15C. and 55C. The polymerization may be short stopped by the addition of agents such as paratertiary-butyl catechol and thiodiphenylamine. The process of polymerization may be either continuous or may be conducted in batch.

Examples of compounds which are useful as modifier according to this invention are di(O-ethyl thionothiolcarbonoxy) sulfide, di(O-ethyl thionothiolcarboxy) disulfide, isopropyl O-ethyl thionothiolcarbonoxy disulfide and so forth. In the compounds of the formula R is a hydrocarbon radical of from one to 8 carbon atoms and R R and R, can be hydrocarbon radicals of from one to 8 carbon atoms or as defined above. The hydrocarbon radicals can be acyclic, cycloaliphatic, ar-' omatic or combinations thereof. For example, the radicals can be methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, n-pentyl, 2-ethyl hexyl, cycloaliphatic radicals having 5 or 6 carbons, aryl radicals such as phenyl, al-

4 karyl radicals such as methylphenyl, combinations thereof and so forth.

The polychloroprenes produced utilizing the modifiers of this invention can be cured and compounded by a variety of agentsand means. The processing and compounding of polychloroprenes is discussed in the Encyclopedia of Polymer Science and Technology, Vol. 3,

p. 724-730 (lnterscience 1965) and J. C. Carl, Neoprene Latex, 1962, which references are incorporated by reference. Accelerators may be such as thioureas, amines, guanidine, thiazole, thiuram sulfides, thiocarbonates, organic acids, sulfur and the like.

It has been discovered that chloroprene polymers produced with the modifiers of this invention have excellent properties including high tensile strength and modulus properties. The polymers also have excellent aging stability and can exhibit excellent characteristics as measured by die swell, easy processing, controllable Mooney Viscosities, cure rate, elongation, crystallization rate, oil resistance and the like. The polymers can be used for a variety of applications either as a latex or as a recovered polymer including such applications as for dipped goods, adhesives, coatings, non-woven fabrics, bonded fibers, treated paper, sealants, foam, thread, carpet backing, hoses, gaskets, elasticized concrete and other known uses of polychloroprenes.

The sulfur modifiers of this invention can be substituted in equal weights for the xanthogen disulfide modifiers in the processes and products as disclosed in US. Pat. Nos. 2,567,] 17; 3,190,865; 3,300,433; 3,317,451; 3,392,134; 3,397,173; 3,444,152; 3,507,825; 3,655,827; 3,686,156; Ger. *OffenwNo.

2,150,156 0.5. application Ser. No. 78,932 filed Oct.

7, 1970) which references are herein incorporated by reference. i v

In the Examples all parts are by weight unless expressed otherwise. These examples are only illustrative of the invention.

EXAMPLE 1 The polymerizations are run in a 5 liter glass autoclave equipped with a paddle agitator. The charge is based on parts of chloroprene which is 2,000

grams.

Polymerization Charge Gone. in Parts by Weight Chloroprene A disproportionated wood rosin, purified by distillation and sold by Hercules Powder Co.

PUMPED CATALYST A catalyst solution of the same composition as the initial catalyst is pumped as required to maintain the polymerization rate.

The polymerization is carried out under a nitrogen blanket at a temperature of 40C. At 69 percent conversion the reaction is short-stopped wtih an'em'ulsio'n' containing 0.02 parts 4-t-butyl cateehol, 0.02 parts pheno-thiazine, 0.8 parts chloroprene, 0.02 parts sou dium dodecyl benzene sulfonate, and 0.8 parts deionized water. The latex is steam stripped of unreacted' monomer and the resulting latex mixture is acidified to a pH of 6.3 using a 10% acetic acid solution and isolated by freeze roll.

Example 1 is a comparative example utilizing n-dodecyl mercaptan as the modifier. Example 2 is a comparative example utilizing diisopropyl xanthogendisulfide as the modifier. Examples 3 and 4 illustrate'the presen invention.

v Raw Mooney (ML 1 +2) Modifier n-Dodecyl mercaptan Diisopropyl xanthogen disulfide Di-(O-ethyl dithiocarbonoxy) sulfide Di-(O-ethyl dithiocarbonoxy) disulfide Samples of the isolated polymers are compounded using the following recipe:

Parts by Weight Polymer l Stearic Acid 0.5 Magnesium Oxide 4 Zinc Oxide Phenyl-a-Naphthylamine 2 OFF Carbon Black 29 Accelerator Components as indicated Samples are cured for 2 0 minutes at 307F and give the following properties? tensile Modulus at Elonga- Ex. Accelelongation, psi strength. tion erator 200 300 40 psi 1 CRA. I120 2200 f- 3060 3140 4l0 2 CRA I320 2440 3230 390 3 CRA 1400 2580 3300 380 4 .CRA 1430 Y 2630 3340 380 l TA-l l" 750 I380 1930 3170 640 2 TA-ll 950 I770 2600 3430 550 3 TA-ll 1230 2210 3060 3530 470 4 TA-ll l 180 2l90 3070 3470 470 The modifier levels are varied to produce polymer with comparable Mooney values. t

'Cl ZA is ethylene thiourea which is Pennac CRA produced by Pennwalt Corp. 'l'A-ll is is treated amine accelerator produced by E. l. Du Pont.

Examples 3 and .4 illustrate that the modifiers of this invention give higher modulus and tensile strength as compared to polymers produced with mercaptans or dialkyl xanthogen disulfides.

EXAMPLE 5 The apparatus and procedure of Example l'is used with the noted changes. The modifier is n-propyl(oethyl dithiocarbonoxy) sulfide. The charge is based on 100 partsof chloroprene which is 2000 grams.

Polymerization Charge Cone. in Parts by Weight Chloroprene v 2.6-ditertiary-butyl para-cresol 0.l Resin-7H5 3.047

2.5 of TAll or CRA -continued Polymerization Charge Conc. in Parts by Weight Deionized Water 100.0 Sodium hydroxide (lOO percent) 7 0.57

Modifier 2.0 Sodium Sulfite 0.30 Sodium Salt'of Condensate of 0.7 formaldehyde and Naphthalen'esulfonic Acid (Lomar PW) Initial Catalyst Potassium Persulfaie 4.500

Silver Salt 0.1 15

Deionized Water 9 Pumped Catalyst A catalyst solution of the same composition as the initial catalyst is pumped as required to maintain the polymerization rate.

The polymerization is carried out under a nitrogen blanket at a temperature of 40C and is short stopped and recovered as in Example 1.

The recovered polymer is loaded with carbon black and cured with ethylene thiourea to give a high tensile strength product.

EXAMPLE 6 The apparatus and procedure of Example 1 is used with the noted changes. The modifier isdi-(N, N- diethyl dithiocarbamyl)-disulfide. The charge is based on parts of chloroprene which is 1000 grams.

Polymerization Charge Cone. in Parts by Weight Chloroprene 100.0 2.6-ditertiary-butyl para-cresol 0.1

Resin-7315* 3.047 Deionized Water [000 Sodium hydroxide (100 percent) 0.57

Modifier [.0 Sodium Sulfite 0.30 Lomar PW 0.70

Initial Catalyst Potassium Persulfate 4.500 Silver Salt .l 15 Deionized Water 95.4

Pumped Catalyst EXAMPLE-S 7 to 13 The procedure of Example 3 is repeated with the substitution' of the indicated modifier for the modifier of Example 3 on an equal molar weight.

Example 'Modifier 7 8' SI SI ymer havng unexpectedly high Mooney scorch time as 8 compared to closely related materials.

TABLE Monsanto Rhcomete r Raw Aged Mooney Shore A Modulus, Tensile 7: Minimum Scorch Torque at Optimum Optimum Mooney Mooney Scorch Hardness psi Strength Elonga- Torque mins. 30 mins. (T Torque Time ML2%+4 3 Day mins. 200% 300% psi tion inch lbs. inch lbs.

S S The compounds of the examples are only illustrative 9 C of the invention. The R groups of the structural formu- C l las listed in the specification may be substituted with non-hydrocarbon radicals which do not interfere with O the modification process. For example, in some in- H stances radicals such 5 halogen, hydroxyl and/or nitrate CH= CH OTC S C O CH CH groups may be present. However, the hydrocarbon s compounds are preferred. Also preferred are the coms o for H H CH3 pound f the mula I T H R, 0-C-S(S)...S do-R 12 cm. H-cH, o-c-s,-c-cH, H-CH;.

Ha Ha wherein m is l to 4, R and R are independently selected hydrocarbon radicals having 1 to 8 carbon atoms, particularly preferred compounds are those of IS cu -cu, o-d' s,,-cH,-cH the formula i ii R 0-C-S,,-C 0 R EXAMPLE 14 The procedure and apparatus of Example 1 is utilized with the noted exceptions. The modifier is di-(O-isopropyl dithiocarbonoxy)-sulfide. The charge is based on 100 parts of chloroprene which is 2000 grams.

Polymerization Charge Conc. in Parts by Weight Chloroprene I00 2,6-ditertiary-butyl para-cresol O.l

Resin-73lS 3.047 Deionized Water 100 Sodium hydroxide (100 percent) 0.57 Modifier 0.76 Sodium Sulfite 0.30 Lomar PW 0.7

Initial Catalyst Potassium Persulfate 0.35 Silver Salt 0.07 Deionized Water 99.6

Pumped Catalyst wherein n is 3 or 4, R and R are hydrocarbon radicals,

but the two R groups do not necessarily have to be the same. Particularly preferred are compounds where R is isopropyl such as di(O-isopropyl dithiocarbonoxy)-sulfide.

The invention claimed is:

l. A process for the emulsion polymerization of chloroprene which comprises polymerizing chloroprene in the presence of from about 0.05 to 5 parts by weight per parts of polymerizable monomer of a modifier having the formula wherein R, is a hydrocarbon radical having from I to 8 carbon atoms, R is a hydrocarbon radical having I to 8 carbon atoms and m is l to 4.

2. A process for the emulsion polymerization of chloroprene which comprises polymerizing chloroprene in the presence of from about 0.5 to 5 parts by weight per 100 parts of polymerizable monomer of a modifier having the formula wherein R is a hydrocarbon radical having 1 to 8 carbon atoms, R', is a hydrocarbon radical having 1 to 8 carbon atoms and n is 3 to 4. I

3. The process of claim 2 wherein the said modifier is of the formula CH 5 5 4. The process of claim 2 wherein the said modifier is H H I of the formula cH C -C s,,-C- 0 C CH,.. f f 

1. A PROCESS FOR THE EMULSION POLYMERIZATION OF CHLOROPRENE WHICH COMPRISES POLYMERIZING CHLOROPRENE IN THE PRESENCE OF FROM ABOUT 0.05 TO 5 PARTS BY WEIGHT PER 100 PARTS OF POLYMERIZABLE MONOMER OF A MODIFIER HAVING THE FORMULA
 2. A process for the emulsion polymerization of chloroprene which comprises polymerizing chloroprene in the presence of from about 0.5 to 5 parts by weight per 100 parts of polymerizable monomer of a modifier having the formula
 3. The process of claim 2 wherein the said modifier is of the formula
 4. The process of claim 2 wherein the said modifier is of the formula 